Staple driver with convex edge and pointed protrusions at the ends

ABSTRACT

A staple driver ( 9 ) is provided, which is adapted to be mounted in a stapler for driving staples into a sheaf of papers ( 11 ) in order to drive, in a striking motion, the legs of a U-shaped staple ( 10 ) through the sheaf of papers ( 11 ). The driver ( 9 ) has a plate-shaped portion ( 13 ) with an edge surface ( 14 ) which is arranged, in the striking motion, to be applied and pressed against the web portion of the staple ( 10 ). The staple driver ( 9 ) has pointed projections ( 12 ) which are arranged to engage, in the striking motion, with the web portion of the staple ( 10 ) in front of the legs of the staple. The edge surface ( 14 ) of the driver ( 9 ) extends in its longitudinal direction along an outwardly curved arc.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a staple driver which is adapted to bemounted in a stapler for driving staples into a sheaf of papers to ejecta U-shaped staple and drive its legs through the sheaf of papers in astriking motion, the striking motion being directed perpendicular to theweb portion of the staple, said driver having a plate-shaped portionwith an edge surface whose width is essentially equal to the thicknessof the staple and which is arranged, in the striking motion, to beapplied and pressed against the web portion of the staple.

2. Description of Related Art

In prior-art staplers, use is made of a magazine which either containsstraight wire staple blanks which are juxtaposed and releasablyinterconnected to form a strip of staple blanks, or contains U-shapedstaples which are arranged closely together in a long row. In the formercase, the stapler has a shaper as well as a driver. As stapling iscarried out by means of the stapler, the strip of staple blanks isadvanced step by the step to the shaper which in a striking motionshapes the straight staple blank, which is in a shaping position, to aU-shaped staple. This U-shaped staple is advanced by the step-by-stepadvancing of the strip to a driving position in front of the driver,which in a striking motion releases the staple from the strip and drivesits legs into a sheaf of papers. In the latter case, i.e. when themagazine contains U-shaped staples, shaping need, of course, not takeplace. The stapler then has no shaper but a driver which operates in thefashion described above.

A prior-art driver and the manner in which it drives a U-shaped stapleinto a sheaf of papers will now be described with reference to FIGS.1A-1F.

FIGS. 1A-1F show a portion of a staple driver 1 which consists of ametal plate having essentially the same thickness as the U-shaped staple2 which is to be driven into a sheaf of papers 3. The driver 1 isarranged in a stapler (not shown) reciprocating in the direction of thedouble arrow P1.

The staple driver 1 has at its side edges projections 4 projecting inthe direction of the staple 2. The projections 4 are pointed and eachlocated in front of one of the two legs 2″ of the staple 2 arranged inthe driving position, so as to engage with the web portion 2′ of thestaple 2 in front of the legs 2″ as the staple 2 is being driven in. Thedriver 1 also has a portion 5 located between the projections 4 andhaving an edge surface 6 facing the staple 2.

The stapler also has a clinching mechanism which comprises two clinchingmeans 7 each of which is turnable on a pivot 8 which is perpendicular tothe plane of the staple 2, and each of which is arranged to cooperatewith a leg 2″ of the staple 2.

When the staple driver 1 in a striking motion is moved in the directionof the staple 2, its two pointed projections 4 will engage with the webportion 2′ of the staple 2 in front of the legs 2″. The projections 4bite into the web portion 2′, the edge surface 6 of the portion 5 of thedriver 1 being applied and pressed against the web portion 2′ in orderto drive, during the continued striking motion of the driver 1, the legs2″ through the sheaf of papers 3 until the web portion 2′ comes intoabutment against the upper side thereof (see FIG. 1C). When the staplelegs 2″ are driven through the sheaf of papers 3, they strike againstthe clinching means 7 arranged in a first turning position and are bentslightly towards each other (see FIG. 1C). The driver 1 is retained inthe position shown in FIG. 1C, and the clinching means 7 are turned to asecond turning position (FIG. 1D) while they bend the staple legs 2″further into abutment against the underside of the sheaf of papers 3,i.e. to a position in which the legs 2″ extend parallel with the sheafof papers 3. Subsequently the clinching means 7 are turned back to thefirst turning position while the driver 1 is retained in its positionwith the edge surface 6 pressed against the web portion 2′ of the staple2 (FIG. 1E). Finally, the driver 1 is returned to its starting positionshown in FIGS. 1A and 1F.

When the staple 2, as is usually the case, is made of a metal wire, itcan, after completion of driving and clinching, be deformed somewhat inthat the staple legs 2″ spring out a distance from the underside of thesheaf of papers 3 in the manner shown in FIG. 1F. This results in thestaple 2 obtaining a considerably greater thickness, seen in the drivingdirection of the staple, than in the clinched position shown in FIG. 1E.This increase in thickness is of course not desirable. For instance, itcauses trouble when a plurality of sheaves of an arbitrary number ofstapled sheets of paper are inserted in a file since the thickness ofthe entire sheaf will be considerably much greater in the upper leftcorner where the staples are usually arranged when stapling togethersheets of paper. Moreover, there is a great risk of the user being tornby the projecting leg ends.

The object of the present invention is to provide, in view of thatstated above, a staple driver which eliminates the above problems causedby the resilience properties of the staple material.

SUMMARY OF THE INVENTION

According to the invention, this object is achieved by a staple driver,which is of the type mentioned by way of introduction, being given thedistinctive features defined in claim 1, i.e. that in combination withthe feature known per se that the staple driver has pointed projectionswhich are arranged to engage, in the striking motion, with the webportion of the staple in front of the legs of the staple, it has thefeature that the edge surface in its longitudinal direction extendsalong an outwardly curved arc.

The edge surface preferably is of essentially the same length as the webportion of the staple and is preferably arcuate over its entire length.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail with reference to theaccompanying drawings, in which

FIGS. 1A-1F show a portion of the prior-art staple driver describedabove, and

FIGS. 2A-2F illustrate a portion of a staple driver according to thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The staple driver 9 of which a portion is shown in FIGS. 2A-2F consistsof a metal sheet which has essentially the same thickness as theU-shaped staple 10 which is made of metal wire and which is to be driveninto a sheaf of papers 11. The driver 9 is arranged in a stapler (notshown) reciprocating in the direction of the double arrow P2.

The staple driver 9 has at its side edges projections 12 projecting inthe direction of the staple 10. The projections 12 are pointed and eachpositioned in front of one of the two legs 10″ of the staple 10 locatedin the driving position, in order to engage with the web portion 10′ ofthe staple 10 in front of the legs 10″, when driving in the staple 10.The driver 9 also has a portion 13, which is located between theprojections 12 and has an edge surface 14 facing the staple 10. The edgesurface 14 has essentially the same length as the web portion 10′ of thestaple 10 and extends in its longitudinal direction along an outwardlycurved arc. In the shown, preferred embodiment, the edge surface 14 isarcuate over its entire length.

The stapler also has a clinching mechanism which comprises two clinchingmeans 15 which are turnable on a pivot 16 each, which is perpendicularto the plane of the staple 10, and are each arranged to cooperate withone of the legs 10″ of the staple 10.

When the staple driver 9 in a striking motion is moved in the directionof the staple 10, its two pointed projections 12 will engage with theweb portion 10′ of the staple 10 in front of the legs 10″. Theprojections 12 bite into the web portion 10′, the edge surface 14 of theportion 13 of the driver 9 being applied and pressed against the webportion 10′ in order to drive, during the continued striking motion ofthe driver 9, the legs 10″ through the sheaf of papers 11 until the webportion 10′ comes into abutment against the upper side thereof (see FIG.2C). The web portion 10′ of the staple 10 will then be given the arcuateshape defined by the edge surface (see FIGS. 2C-2E). When the legs 10″are driven through the sheaf of papers 11, they strike against theclinching means 15 placed in a first turning position and are bentslightly towards each other (see FIG. 2C). The driver 9 is retained inthe position shown in FIG. 2C and the clinching means 15 are turned to asecond turning position (FIG. 2D) while they bend the staple legs 10″further into abutment against the underside of the sheaf of papers 11,i.e. to a position in which the legs 10″ extend parallel with the sheafof papers 11. Subsequently, the clinching means 15 are turned back tothe first turning position while the driver 9 is retained in itsposition with the edge surface 14 pressed against the web portion 10′ ofthe staple 10 (FIG. 2E). Finally, the driver 9 is returned to thestarting position shown in FIGS. 2A and 2F.

When the staple driver 9 has left the staple 10 which has been driven inand clinched, the web portion 10′ thereof springs back and becomesstraight while at the same time the staple legs 10″ at their free endsare pressed a distance into the sheaf of papers 11 at the undersidethereof (see FIG. 2F). As a result, the above-described outwardsspringing of the staple legs from the underside of the sheaf of papersdoes not take place, in contrast to the prior-art staple driver (seeFIG. 1F).

What is claimed is:
 1. A staple driver for use in a stapler having aclinching device which bends legs of a U-shaped staple of the typehaving a web portion and two legs depending from said web portion, saidstaple driver comprising: a plate-shaped portion having an edge surface,a width of said edge surface being essentially equal to a thickness of astaple to be driven; a pair of pointed projections disposed at outerends of said edge surface, said pointed projections being spaced apartat a distance such that they are arranged to engage the web portion ofthe staple substantially directly above the legs of the staple, andwherein a portion of said edge surface between said pair of pointedprojections is shaped as an outwardly curved arc.
 2. A staple driver asclaimed in claim 1, wherein the edge surface is arcuate over its entirelength between said pair of pointed projections.
 3. A stapler fordriving staples into a sheaf of papers, comprising: a staple driver soconstructed and arranged to eject a U-shaped staple having a web portionand two legs, and to drive said legs of said staple through a sheaf ofpapers in a striking motion, a clinching device constructed to bend thelegs of said staple upon being driven through a sheaf of papers, whereina striking motion of said staple driver is directed perpendicular tosaid web portion of said staple, wherein said staple driver has aplate-shaped portion with an edge surface, a width of said edge surfacebeing essentially equal to a thickness of said staple, and which isarranged, in the striking motion, to be applied and pressed against theweb portion of the staple, and wherein the staple driver has pointedprojections which are so constructed and arranged to engage, in thestriking motion, the web portion of the staple substantially directlyabove the legs of the staple, and said edge surface of said stapledriver is of essentially the same length as the web portion of thestaple, and is curved in an outward arc along a longitudinal directionbetween said pointed projections.
 4. A stapler as claimed in claim 1,wherein the edge surface of the staple driver is arcuate over its entirelength.
 5. A stapler for driving staples into a sheaf of paper,comprising: a staple driver so constructed and arranged to eject aU-shaped staple, said staple having a substantially straight web portionof a predetermined length and having two legs depending from outer endsof said web portion, said staple driver further being so constructed andarranged to drive said legs of said staple through a sheaf of papers ina striking motion, a clinching device constructed to bend the legs ofsaid staple upon being driven through a sheaf of papers, said clinchingdevice being operable to bend free ends of said legs into abutmentagainst an underside of said sheaf of papers, wherein a striking motionof said staple driver is directed perpendicular to said web portion ofsaid staple, wherein said staple driver has a plate-shaped portion withan edge surface,a width of said edge surface being essentially equal toa thickness of said staple, and which is arranged, in die strikingmotion, to be applied and pressed against the web portion of the staple,and wherein said edge surface of said staple driver is of essentiallythe sonic length as the web portion of the staple, and wherein thestaple driver has pointed projections which are so constructed andarranged to engage, in the striking motion, the web portion of thestaple substantially directly above the legs of the staple, and whereinat least a portion of said edge surface extending between said pointedprojections is curved man outward arc to thereby bend said web portionof said staple into a curved shape during said striking motion of saidstaple driver, whereby, upon completion of said striking motion, saidweb portion springs back toward its initial substantially straightshape, causing said free ends of said staple legs to move into tightengagement with said underside of said sheaf of papers.
 6. A method forstapling a sheaf of papers comprising: positioning a U-shaped staple ata desired position relative to an upper surface of said sheaf of papers,said staple having a substantially straight web portion of apredetermined length and having two legs depending therefrom, moving astaple driver toward said staple in a striking motion, said stapledriver having a plate-shaped portion with an edge surface, a width ofsaid edge surface being essentially equal to a thickness of said staple,and a length of said edge surface being of essentially the same lengthas the web portion of the stapler, said edge portion further having apointed projection at each end thereof, and at least a section of saidedge portion between said pointed projections being curved in an outwardarc, engaging said web of said staple With said pointed projections, ina continuation of said striking motion, driving said legs of said staplethrough a thickness of said sheaf of papers bending s free end of eachof said legs protruding past a lower surface of said sheaf of papers,such that said free ends contact said lower surface, bending at least asection of said web portion of said staple with said section of saidedge portion having said outwardly curved shape, and releasing saidstaple driver from said web portion of said staple, whereby a bentsection of said web springs back toward its initial shape, causing saidfree ends of said legs to move into tight engagement with said lowersurface of said sheaf of papers.